formatToDuration.js

const formatToDuration = milliseconds => {
	const seconds = Math.round(milliseconds / 1000);
	const s = Math.round(seconds % 60);
	const m = (Math.floor(seconds / 60) % 60);
	const h = (Math.floor(seconds / 60 / 60) % 24);
	const d = (Math.floor(seconds / 60 / 60 / 24));

	return [
		(d ? `${d}d` : ''),
		(h ? `${h}h` : ''),
		(m ? `${m}m` : ''),
		(`${s}s`),
	].filter(a => a).join(' ');
};